Republican State Rep. Daniel Winslow will not sign on to a "People’s Pledge" barring outside advertising in the Massachusetts U.S. Senate special election.

“I support reforming the way we finance campaigns in this country,” Winslow said in a statement. “But I am surprised with such an urgent need for action in Washington, D.C., that anyone would be wasting time going over old plays that won't produce a single job, a better education, a more secure retirement, a cleaner environment, a lower deficit, or an honest and straightforward way to finance our elections.”

U.S. Reps. Edward Markey and Stephen Lynch, who are competing in the Democratic primary for the Massachusetts U.S. Senate seat, agreed on Wednesday to sign a People’s Pledge similar to the one put in place by Republican Scott Brown and Democrat Elizabeth Warren in the November Senate election. Both Markey and Lynch said they wanted to keep outside money out of the Massachusetts race. The pledge states that if an outside group spends money on advertising for or against either candidate, the beneficiary of the ad will pay 50 percent of the cost of the ad buy to a charity of the opposing candidate’s choice.

But the pledge would only apply during the general election if both the Democratic and Republican nominees agree. “If Winslow doesn't sign, and he is the Republican nominee, then the Pledge would not be in effect, and that would be extremely disappointing,” Lynch spokesman Conor Yunits said. (The pledge would still apply to the Democratic candidates during the Democratic primary campaign.)

A spokesman for Republican Gabriel Gomez said Gomez has not decided whether to abide by the pledge.

Winslow said in his statement, released Thursday, that he would welcome outside advertising. “I welcome any outside group to contribute positive bio or issue ads, mailings, social media and the like,” Winslow said. “I am running a different kind of campaign. I am not an entrenched Washington insider who has to sign a pledge in order to run a fair, clean, positive campaign.”

Winslow added, “For congressmen Markey and Lynch to posture about outside money in politics when their coffers are already filled with money from outside Massachusetts just shows you how inauthentic this pledge really is.”

According to the non-partisan Center for Responsive Politics, around 40 percent of the money Markey has raised in the 2012 election cycle, or around $434,000, has come from political action committees. Lawyers and lobbyists are among the top contributors to Markey, who is the ranking member on the House Natural Resources Committee. The Boston Globe reported that the electronics and communications industries have also been major funders of Markey, who was previously the chairman of the House Subcommittee on Telecommunications. In the 2012 cycle, 31 percent of the money Markey has raised has been from out of state, according to the Center for Responsive Politics.

The Center for Responsive Politics found that 64 percent of Lynch’s contributions during the 2012 cycle, around $464,000, have been from political action committees. Unions are the top contributors to Lynch, particularly from the public sector and building trades. In the 2012 cycle, 17 percent of his money has come from out of state.

Winslow and Gomez have never before run congressional campaigns and have not yet had to file fundraising reports.

Peter Ubertaccio, chairman of the Department of Political Science and International Studies at Stonehill College, said it makes sense that the Democrats would agree to the pledge and the Republicans would not. Democrats are trying to appeal to progressive activists who tend to be more concerned with the influence of money in politics. Additionally, Democrats in Massachusetts are in a better position to raise money than Republicans. “Because it’s viewed as a race that favors the Democratic nominee, money will flow to Democrats easily and a lot of big Republican donors won’t give the Republicans a lot of funds,” Ubertaccio said.

Additionally, candidates like Lynch and Markey already have wide networks in the state, while lesser known Republicans like Gomez and Winslow will have to spend significant sums of money just to gather the signatures necessary to get on the ballot.

Massachusetts Democratic Party Chairman John Walsh said Winslow "just gave in to the far right wing of the Republican party.” “The news today of his refusal to sign the ‘People's Pledge’ makes it clear that he welcomes the right wing attack machine into our state,” Walsh said. “So, when the Karl Rove sleazy ads start airing, voters can thank Winslow. The voters now deserve to know where other Republicans stand on this key reform issue."

However, so far, the only outside national group to get involved in the Massachusetts race is a Democratic-leaning one. The Boston Herald reported that American Bridge 21st Century, a left-wing super political action committee that does opposition research on Republican candidates, requested minutes of all the planning board meetings in the town of Norfolk during the six years that Winslow served on the board, from 1988 to1994.